Colloquium

Upcoming Colloquium

Atomic-scale visualization of topological spin textures
Dr. Jay Gupta, The Ohio State University

September 26, 2022
11:00am in HSCI-102

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Jay Gupta

Spin textures in chiral magnets are of fundamental interest and may enable novel magnetic storage and computing technologies. These spin textures can have a mathematical topology ascribed to them, and our work is focused on exploring the connections between this idealization and textures in real materials. In MnGe, such textures arise from the competition of ferro-magnetic exchange, favoring aligned spins, and a so-called 'Dzyaloshinskii-Moriya interaction' (DMI) which favors perpendicular spins. In our spin-polarized STM studies of MnGe thin films, we study spin textures at the surface, where DMI may arise not only from the chiral 'B20' MnGe crystal structure, but also from the surface itself. Furthermore, the thin film structures allow us to study strain effects, and provide a path for integration into devices.

Our SP-STM images indicate helical stripe domains with a 6 nm period, which micromagnetic modeling helps us understand as a surface projection of the helical wavevector, canted away from the film normal. We can deduce the three-dimensional orientation of the helical wavevectors at domain walls, and we predict that three helical domains can meet in two distinct ways to produce either a 'target-like' or a 'π-like' topological spin texture. Both textures are observed experimentally, and are only found in slightly strained regions of the films. Topological defects in the target texture can be created, moved and annihilated with current/voltage pulsing from the STM tip. The core of the target texture itself can be similarly moved, and can also be reversibly switched with applied magnetic field.

These studies represent an initial step toward understanding the interplay of bulk and surface magnetism in chiral magnets, and the manipulation of these topological spin textures is a promising step toward future spintronics applications.

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magnetic surface at 20 nanometer
Fig. Magnetic surface with 20 nanometer scale bar.

The Colloquium is a unique opportunity for students to learn about new developments in physics and what physicists do after they graduate. Hosted by the Department of Physics and Astronomy at California State University Long Beach, the weekly meetings invite guests from universities, research laboratories, and industry to present and discuss current topics in physics. All students are encouraged to attend for a well-rounded experience and training in physics.

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Schedule

Additional colloquia will be posted as details become available.

Upcoming Colloquia
Date Title Speaker and Affiliation
September 26, 2022 Atomic-scale visualization of topological spin textures Dr. Jay Gupta, The Ohio State University
October 3, 2022 (topic: particle) Mike Brown, Caltech
October 10, 2022 (topic: soft matter) Kevin Freedman, UC Riverside
October 17, 2022 (topic: solid state) Javier Sanchez-Yamagishi, UC Irvine
October 24, 2022 (topic: solid state/quantum) Eli Levenson-Falk, USC
October 31, 2022 (topic: soft matter) Siavash Ahrar, CSU Long Beach
November 7, 2022 (topic: astro/outreach) Sophia Gad-Nasr, UC Irvine
November 14, 2022 (topic: particle) George Fuller, UC San Diego
November 28, 2022 (topic: quantum computing) Grant Salton, Amazon
December 5, 2022 Student Presentations Students, CSU Long Beach

Previous Colloquia

The following colloquia have finished.

Previous Colloquia
Date Title Speaker and Affiliation
September 19, 2022 Fundamental Physics at the Center of Our Galaxy Dr. Tuan Do, UCLA
September 12, 2022 SrCoO3: Stretching and Straining towards new Ferroic Properties Dr. Sara Callori, CSU San Bernardino
August 29, 2022 Meet 'n' Mix All Physics Students and Faculty, CSU Long Beach

The Colloquium Archive has the Colloquia from previous semesters.


Sponsors

We acknowledge with gratitude donations and support from the following present sponsors:

  • H.E. and H.B. Miller and Family Endowment
  • Benjamin Carter
  • American Physical Society
  • Anonymous

We also acknowledge with gratitude our past donors: The Forty-Niner Shops, Inc., The Northrop Grumman Foundation, Sandra Dana, Anonymous.

If you wish to support the Colloquium, please contact the colloquium coordinator or the department chair. Thank you!